Mixed methyl- and propyl-thiolate monolayers on a Au(111) surface

Area of Science:

• Surface Science
• Materials Chemistry
• Nanotechnology

Background:

• Self-assembled monolayers (SAMs) are crucial for modifying surface properties.
• Mixed-thiolate SAMs offer tunable characteristics compared to single-component systems.
• Understanding phase behavior in mixed SAMs is key to controlling nanoscale interfaces.

Purpose of the Study:

• To investigate the formation and structural evolution of mixed methyl- and propyl-thiolate SAMs on Au(111).
• To characterize the phase transitions induced by thermal annealing.
• To explore the potential for creating ordered nanostructures on gold surfaces.

Main Methods:

• Preparation of mixed methyl- and propyl-thiolate SAMs via vapor-phase exposure of Au(111) to methyl-propyl-disulfide.
• High-resolution surface imaging using Scanning Tunneling Microscopy (STM).
• Thermal annealing experiments to induce structural changes.

Main Results:

• A (3 × 4) phase was observed in as-prepared mixed SAMs, containing three distinct thiolate-gold-thiolate configurations.
• Thermal annealing at 373 K caused partial desorption of methyl-thiolate species.
• Annealing resulted in the formation of a striped phase, predominantly composed of dipropyl-thiolate species.

Conclusions:

• Mixed methyl- and propyl-thiolate SAMs can be controllably formed on Au(111).
• Thermal annealing provides a route to induce phase transitions and structural ordering in these SAMs.
• The formation of a propyl-rich striped phase highlights the potential for designing specific nanostructures through thermal treatment.